Colloidal CsPbX3 Nanocrystals with Thin Metal Oxide Gel Coatings

Dominic Guggisberg; Sergii Yakunin; Christoph Neff; Marcel Aebli; Detlef Günther; Maksym V Kovalenko; Dmitry N Dirin

doi:10.1021/acs.chemmater.2c03562

Colloidal CsPbX₃ Nanocrystals with Thin Metal Oxide Gel Coatings

Chem Mater. 2023 Mar 20;35(7):2827-2834. doi: 10.1021/acs.chemmater.2c03562. eCollection 2023 Apr 11.

Authors

Dominic Guggisberg^{1

2}, Sergii Yakunin^{1

2}, Christoph Neff¹, Marcel Aebli^{1

2}, Detlef Günther¹, Maksym V Kovalenko^{1

2

3}, Dmitry N Dirin^{1

2

3}

Affiliations

¹ Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland.
² Laboratory for Thin Films and Photovoltaics, Empa - Swiss Federal Laboratories for Materials Science and Technology, Dübendorf CH-8600, Switzerland.
³ NCCR Catalysis, Institute of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich CH-8093, Switzerland.

Abstract

Lead halide perovskite (LHP) nanocrystals (NCs) have gathered much attention as light-emitting materials, particularly owing to their excellent color purity, band gap tunability, high photoluminescence quantum yield (PLQY), low cost, and scalable synthesis. To enhance the stability of LHP NCs, bulky strongly bound organic ligands are commonly employed, which counteract the extraction of charge carriers from the NCs and hinder their use as photoconductive materials and photocatalysts. Replacing these ligands with a thin coating is a complex challenge due to the highly dynamic ionic lattice, which is vulnerable to the commonly employed coating precursors and solvents. In this work, we demonstrate thin (<1 nm) metal oxide gel coatings through non-hydrolytic sol-gel reactions. The coated NCs are readily dispersible and highly stable in short-chain alcohols while remaining monodisperse and exhibiting high PLQY (70-90%). We show the successful coating of NCs in a wide range of sizes (5-14 nm) and halide compositions. Alumina-gel-coated NCs were chosen for an in-depth analysis, and the versatility of the approach is demonstrated by employing zirconia- and titania-based coatings. Compact films of the alumina-gel-coated NCs exhibit electronic and excitonic coupling between the NCs, leading to two orders of magnitude longer photoluminescence lifetimes (400-700 ns) compared to NCs in solution or their organically capped counterparts. This makes these NCs highly suited for applications where charge carrier delocalization or extraction is essential for performance.